Robin Cook, the former Foreign Secretary, died in hospital last night after collapsing while walking in the Scottish hills he loved.

The 59-year-old MP was airlifted to hospital in Inverness yesterday afternoon after being taken ill while walking with his wife, Gaynor, and friends near the summit of Ben Stack, close to Lochinver, Sutherland.

There were unconfirmed reports last night that he suffered a heart attack and then fell, breaking his neck.

An unnamed friend who was with the MP on the mountain attempted to give Cook mouth-to-mouth resuscitation for 30 minutes before an Coastguard helicopter arrived at the scene.

The helicopter's crew continued efforts to revive Cook on the journey to Raigmore hospital where he was pronounced dead at 4.05pm, shortly after arrival.

Cook, who also leaves two sons, Christopher and Peter, was a dominant intellectual force in New Labour. He sealed his reputation for political integrity with his resignation from the cabinet on the eve of the Iraq war.

His death last night left colleagues in shock, eliciting tributes from across the political spectrum to the man whom John Prescott, the Deputy Prime Minister, described as 'the greatest parliamentarian of his generation'.

Prime Minister Tony Blair was also quick to pay tribute. 'Robin was an outstanding, extraordinary talent - brilliant, incisive in debate, of incredible skill and persuasive power,' he said.

'His contribution to the politics of Britain was hugely significant. His contribution to the Labour Party was immense. He will be missed and mourned by all of us.'

Ironically, friends said Cook had never appeared healthier and happier since leaving office: he was a keen outdoorsman who kept fit by riding and walking.

Gordon Brown, the Chancellor, who had known Cook since they were university students, said his thoughts were with Gaynor and the family.

'With his death so sudden and unexpected, the tragic loss to his family, his constituency, our party and our country is all the greater and is most keenly felt by all of us who knew him and will now miss him greatly,' Brown said last night.

'Robin's mastery of the Commons was acknowledged on all sides and his incisive mind, forensic skills and formidable and wide-ranging debating prowess were seen by the public very clearly when, in opposition, he led the response to the Scott inquiry.'

In an age of image-conscious politicians, the diminutive, ginger-bearded Cook did not cut a fashionable figure, but his fiercely burning intellect propelled him to the heights of the New Labour firmament, earning the respect even of his foes.

He was admired by his civil servants for the apparently effortless speed with which he mastered his briefs and his constant hunger for ideas, but he was also a cultured man, as happy to discuss Victorian novelists as the season's racing form.

Despite forging a career on the back benches as a quietly devastating critic of foreign policy, tribal loyalty saw him return to the fold to campaign for Tony Blair's re-election in May.

Occasionally given to prickliness, Cook was not always an easy man, but his dry wit and sense of mischief endeared him to friends. He spoke movingly of how marriage to his second wife, his former secretary Gaynor Regan, had changed him, teaching him 'emotional intelligence' and giving him an ability to relate to others' feelings.

Born in Bellshill in February 1946, Robin Cook went to school in Aberdeen and Edinburgh before going on to read English literature at Edinburgh University - where he met his first wife, Margaret, a consultant haematologist.

He became an MP in 1974, rising swiftly through the opposition ranks, and when Labour gained power in 1997, was appointed Foreign Secretary, devising the ethical foreign policy that crystallised the optimism of the early New Labour years.

His proudest achievement in office, he said, was when Britain intervened to halt ethnic cleansing in Kosovo.

After the 2001 general election, he was moved abruptly sideways to Leader of the Commons, a job he did not initially want but which became a showcase for his wit - and his tenacious pursuit of House of Lords reform.

'It's hard to think of anyone who matched him over the dispatch box - he had such a formidable mind,' said Stephen Twigg, his deputy during those years.

In the rare moments that he relaxed, however, Cook could be great company.

'He was hugely funny. I remember we had a Christmas night out - it ended up being in about February. He took us all to a jazz club in Camden; he loved jazz,' Twigg added.

Denis MacShane, the former Europe minister who also worked closely with Cook, said his thoughts were with Cook's wife and family. 'Robin has illuminated British politics, and especially those of the democratic left, for more than 30 years,' he said. 'Even half an insight from Robin was worth 10 speeches from most politicians.'

Local emergency services started to receive reports just after 2.30pm yesterday that the Livingston MP had collapsed near the summit of Ben Stack, 2,365ft above sea level.

As Cook's friends waited for the Coastguard helicopter to arrive, they were given guidance on resuscitation techniques by medical experts via telephone.

The helicopter's crew then battled to revive him using cardio-pulmonary resuscitation equipment, before airlifting the unconscious politician to Raigmore hospital. Cook's wife was rushed by police car to the hospital where she watched as doctors unsuccessfully attempted to save his life.

Cook was a keen hill-walker, and regularly spent his summer holidays with close family and friends enjoying the dramatic mountain scenery of Highland Scotland, rather than going abroad.

The announcement of his death was delayed for three hours as police contacted relatives.

Last night, friends of Cook said his demise had left a huge gap in British politics. 'His death leaves a gaping hole in the leadership of the Labour movement.' said Tony Woodley, general secretary of the Transport and General Workers' Union.

'He was a socialist and an internationalist of principle and we are all left poorer by his passing,'.

Former deputy Labour leader Roy Hattersley said Cook's death would be felt keenly in the House of Commons.

'I don't think there has been any parliamentarian of my time who has made more significant speeches,' Hattersley said.